In the drilling of an oil or gas well it is conventional to employ a drilling rig to power a rotary, hollow drill pipe at the lower end of which is a drill bit which is advanced downwardly into the earth. Operation of the drilling apparatus is accompanied by the delivery of water to the upper end of the drill pipe and under such force as to cause the water to flush the cuttings from the bottom of the bore and return and carry them to the surface. Conventionally, the water is supplemented with clayey material commonly referred to as drilling mud. The drilling mud may contain a number of ingredients, including fresh or salt water, so as to render the mud sufficiently plastic to flow while retaining sufficient body or viscosity to effect sealing of the walls of the well bore and to maintain in suspension the drill cuttings as the latter are moved upwardly of the well bore. Typical muds are provided by Wyoming bentonite or sodium montmorillonite. Another clay commonly used for mud is attapulgite.
The particular kind of clay or similar substance used for a drilling mud will depend upon a number of factors which are of no particular significance to the method herein disclosed. All of the materials used for drilling muds, however, have the common characteristic that, when the drilling operations are completed, the spent muds are agglomerated with well cuttings and liquids, usually brine, in a semi-solid slurry or mass having no form stability or structural strength and a consistency similar to that of toothpaste with a funnel test viscosity of between about 40 to 60 sec./l.
At the completion of well drilling operations a large quantity of the agglomerated materials must be disposed of. These materials may not simply be scattered about the well site, or even collected in a pit adjacent the drilling site, for several reasons. One reason is that the chlorides from the brine will contaminate the soil and adjacent ground waters. Another reason is that, since the agglomeration has no appreciable stability, it is not possible to restore the ground to the condition it had prior to the excavation of the pit. That is, excavated earth cannot simply be returned to the pit with the agglomerated materials inasmuch as the latter would ooze from the pit and result in the formation of a quagmire.
Because of the difficulties encountered heretofore in disposing of well cuttings and materials associated therewith at the well site, it has been the practice to load such materials in tank trucks and transport them to a central disposal site. The time and expense of such practice make the cost of such disposal exorbitant.